Temporal changes in chromosome abnormality rate in human spontaneous abortions: evidence for an association between sex-chromosome monosomy and trisomy 16.

As part of a cytogenetic survey of human spontaneous abortions, the relative frequencies of different categories of chromosome abnormalities were evaluated for possible temporal changes. Three classes of chromosome abnormalities showed significant linear trends; sex-chromosome monosomy and tetraploidy decreased over the study period, while trisomy increased. The increase in trisomy was largely attributable to trisomy 16, which showed a two-fold increase over the duration of the study. The linear increase in trisomy 16 was inversely related to sex-chromosome monosomy. This effect was restricted to women over 30 yr of age and was most pronounced among Oriental women.